Vol. 12: 129–136, 1999
CLIMATE RESEARCH
Clim Res
Published August 27
Coastal zone of The Gambia and the Abidjan
region in Côte d’Ivoire: sea level rise vulnerability,
response strategies, and adaptation options
Bubu P. Jallow 1,*, Sekou Toure 2,**, Malang M. K. Barrow 3, Assa Achy Mathieu 4
2
1
Department of Water Resources, 7 Marina Parade, Banjul, The Gambia
Ecole Nationale Superieure des Travaux Publics, Yamoussoukro, Côte d’Ivoire
3
National Environment Agency, 5 Fitzgerald Street, Banjul, The Gambia
4
Physics Department, University of Cocody, Abidjan, Côte d’Ivoire
ABSTRACT: The aerial videotape-assisted vulnerability analysis (AVVA) technique was combined
with various data sets to assess the vulnerability of the coastal zone of The Gambia to sea level rise.
Land loss due to inundation, flooding, and erosion was estimated. Costs of damage and population at
risk were also evaluated. Only historical data and maps were used to assess the vulnerability of the
coastal zone of the Abidjan region of Côte d’Ivoire to sea level rise. Results show that with a 1 m sea
level rise the whole of the capital city of Banjul will be under mean sea level in the next 50 to 60 yr as
a greater part of the city is below 1 m. The mangrove systems on St. Mary’s Island, Kombo St. Mary, and
the strand plains in the north bank will be inundated. About 1950 billion Dalasis (US $ 217 million)
worth of land will be lost. The most appropriate response would be to protect the whole of the coastline
of Banjul, the shoreline area from the Banjul cemeteries to Laguna Beach Hotel, the infrastructure at
Sarro, and the hotel complex at Cape Point. Innovative sand management, repair of the damaged
groins, and construction of dikes, breakwater structures, revetments, and low-cost seawall are some of
the shoreline stabilization and hardening techniques suggested for the protection of this area. For the
Abidjan region, the same response strategies should be used. Adaptation responses identified for both
regions include public awareness, increase in height of coastal infrastructure, urban growth planning,
wetland preservation and mitigation, and development of a coastal zone management plan.
KEY WORDS: Erosion · Inundation · Land loss · Mangroves · Vulnerability analysis · Bruun Rule
1. INTRODUCTION AND BACKGROUND
INFORMATION ON THE COASTAL ZONE
The coastal zone of The Gambia extends 80 km from
Buniadu Point and the Karenti Bolong in the north to
the mouth of the Allahein River in the south (Fig. 1). It
has 70 km of open ocean coast and about 200 km of
sheltered coast along the River Gambia. The sheltered
coast is dominated by extensive mangrove systems
(66 900 ha) and mud flats.
Only about 20 km of the coastline is significantly
developed, and this includes Banjul (the capital city),
**E-mail: [email protected]
**Present address: High Commissioner for Hydraulics, Abidjan, Côte d’Ivoire
© Inter-Research 1999
Bakau and Cape St. Mary, Fajara, and the Tourism
Development Area (TDA). Thirteen hotels and tourist
resorts have been built on this stretch of the coastline.
Elsewhere, the coastline is largely underdeveloped,
except for some fish landing sites and cold storage
infrastructure used to process and store fish and
shrimp. The coastal zone contributes significantly to
the economy of The Gambia. From October to May,
The Gambia receives more than 100 000 tourists, all
beach resorts and hotels are operational, and the
industry employs about 7000 persons either directly or
indirectly.
The region of Abidjan is situated in Southeast Côte
d’Ivoire with a surface area of about 12 180 km2 and is
composed of the districts of Abidjan, Agboville, Tiassale, and Grand-Lahou. The population is over 2 mil-
130
Clim Res 12: 129–136, 1999
land. This zone is composed mainly of lagoons and
streams. (2) An intermediate zone with low relief. (3)
The hinterland with relatively high altitudes of 50 to
200 m.
2. ASSESSMENT METHODOLOGY AND DATA
USED IN THE ASSESSMENT
Fig. 1. Coastal zone of The Gambia
lion inhabitants, and the population density is high
(80 persons km–2). Hydrologically, the region is drained
by the Bandama River and other streams such as Ira
and Agneby (Delor et al. 1992). In the east-west direction, the drainage is by Ebrie Lake, into which most
small rivers empty. The climate of the Abidjan region is
equatorial, having 2 rainy seasons separated by 2 dry
seasons. Rainfall decreases in the south-to-north direction from 2100 to 1400 mm per annum. The variation in
temperature is low, with fluctuations between 24 and
27°C.
In this region lies the capital city of Abidjan, which is
highly metropolitan. Important economic activities and
infrastructure of the region include: (1) The establishment and management of vast rubber, pineapple, oil
palm, and coconut plantations. (2) The Port of Abidjan,
which provides facilities for trading with the rest of the
world. Access to the ocean is provided by the Vridi
Canal. (3) Ocean fisheries, which remain the main
activity of the coastal population. (4) Important 4-lane
highways, which run in the southeast-to-northwest
direction. (5) Both national and international air transport provided at the Abidjan International Airport at
Port Bouet.
The region can be divided into 3 geomorphologic
units in a south-to-north direction. These are: (1) The
shoreline linking the Atlantic Ocean with the main-
2.1. Data sets. Various data sets for the coastal zone
of The Gambia and the Abidjan region were assembled to inventory and characterize the study areas. The
data and information collected included black-andwhite and colour infrared aerial photographs, and
topographic, geological, and bathymetric maps of both
study areas. Also available were contoured orthophoto
maps of the 1982 aerial photography for the Gambian
coastal zone. Still photographs from different years
showing some of the damage caused by erosion were
also available from the Oceanography Centre of Côte
d’Ivoire and the Department of Water Resources of The
Gambia.
Documentation of past similar studies was undertaken, and, to augment the data and information on the
Abidjan study area, it was necessary to interview some
people. Those interviewed included residents close to
the coastline of Abidjan, contractors working for a project on the construction of a breakwater west of the
Vridi Canal, the coastguards at the Vridi Canal, and
some staff of the Oceanography Centre.
A low-level (~150–200 m) video record of both the
open and sheltered coasts of The Gambia was
acquired, but due to logistics and time constraints, this
was not possible in the Abidjan study. The video
record was obtained as part of the aerial videotapeassisted vulnerability analysis (AVVA) technique
(Leatherman et al. 1995). From the video record, it is
possible to determine the type of coast, land use, land
cover, and infrastructure.
Socio-economic data (GDP, GNP, and so forth), along
with information on annual number of tourists and outof-pocket expenditures, fish landing and catch by
species, wetland habitats, and historic and cultural
assets, were also available. The Department of Physical Planning also made available the value of land
along the coast.
2.2. Methodology. The impact assessment procedure used in both studies follows the AVVA technique
and the IPCC Common Methodology, but it was not
possible to conduct video recording of the Abidjan
region. AVVA is a new, rapid, and low-cost technique
that involves the combination of (1) obliquely videotaping the coastline at low altitude from a small airplane and (2) carrying out archival research (Leatherman et al. 1995). Combining the video record and the
131
Jallow et al.: Sea level rise vulnerability of The Gambia and Côte d’Ivoire
historical data, it was possible to assess, both qualitatively and quantitatively, some of the potential impacts
of a 1 m sea level rise. The assessment involves the
characterization of the study area, determination of sea
level scenarios, estimation of land loss and other damage, translation of this damage to monetary terms, and
identification of response strategies and adaptation
options.
2.2.1. Characterization of the coastal zone: Based on
the assembled data, it was possible to characterize the
coastal zone of the 2 study areas. The coastal zone of
The Gambia was characterized into the 9 units shown
in Fig. 1. Each unit contains 1 or a combination of
coastal types. A detailed description of these units is
contained in Jallow et al. (1996). Some of the units
are based on the UNEP/OCA PAC Report (Quelenec
1988). The coastal zone of the Abidjan region was characterized into 2 units: west and east of the Vridi Canal.
2.2.2. Sea level rise scenarios: Tide gauge records
available for both study areas cover only a short period
of time, and long-term geological data suggest insignificant tectonic variations. Hence, the global sea
level rise scenarios that have been widely adopted in
the IPCC documentation (IPCC 1990, Pepper et al.
1992) are used. These scenarios are the current rate of
sea level rise of 0.2 (no acceleration), 0.5, and 1.0 m
century–1. Where the variation of the land formation is
relatively smooth, the 0.5 m contour of land inundation
was interpolated from the 1.0 m contour line on the
coastal map series.
2.2.3. Estimation of land loss and damage: Of primary concern is to determine how much land will be
lost due to sea level rise. On the sheltered coasts and
where the open coast is characterized by spits or barriers backed by marshes and mangroves and, in some
places, strand plain type of coast, the drowning or permanent submergence (inundation) concept of land loss
was used as the initial potential impact. After inundation, erosion of the open coast continues due to wave
action, and the Bruun Rule is used to determine the
retreat of the land.
The area likely to be inundated was delineated on
the topographic maps by estimating the 1 m contour
line. Land loss due to the lower (0.2 m) scenarios was
estimated by linear interpolation from the amount of
loss due to the 1 m sea level rise. The percentage loss
for intermediate (0.5 m) scenarios was then linearly
interpolated.
Land loss due to wave action is estimated using the
mathematical definition of the Bruun Rule given in
Hands (1983) as
R = G[L/(B + d )]S
(1)
*
where R is the shoreline retreat (erosion) due to a sea
level rise S (scenario) above mean sea level, d is the
*
depth of closure, B is the dune/cliff height, L is the
width of the active profile, and G is the inverse of the
overfill ratio of the material being eroded. Fig. 2 shows
the relationship of the parameters for the Bruun Rule.
G can be safely taken to be 1 as sand is predominant
on the open ocean coast of both study areas, and,
hence, it is assumed that all the eroded material will
remain within the active beach/near-shore profile.
Where this assumption is not valid, some of the eroded
material that is fine-grained (clay and silt) is lost to
deeper water; so greater recession than reported
would be expected.
d is determined using a range of techniques that
*
include grain size trends, the orientation of offshore contours, and a wave-based approach. According to
Nicholls et al. (1995), it is best to use the wave-based
approach, as this can be directly related to time scale.
Various studies conducted so far on the estimation of the
potential impacts of sea level rise used the low and high
estimates of closure depth, which, according to Nicholls
et al. (1995), will embrace the actual depth of closure.
For the Gambian study area, d is taken from Dennis
*
et al. (1995) and assumed to be d (L,1) = 3.4 m for the
*
analysis of annual change and d (L,100) = 5.9 m over a
*
century. The depth of closure for the 100 yr period was
calculated from the annual depth of closure as:
d
= 1.75d (L,1)
(2)
*(L,100)
*
where the coefficient (1.75) is based on Hands (1983).
L was determined at different locations along the
coast using bathymetric maps. Since the coastline of
The Gambia shows varying beach width and dune and
cliff heights, the Bruun Rule was applied to similar segments following the characterization of the coastline.
For the Abidjan Region of Côte d’Ivoire, the annual
depth of closure d (L,1) was calculated using the wave
*
methodology defined as:
= 2.28H – 68.5(H 2/gT 2)
(3)
*(L,1)
where H is the annual exceeded wave height in a
12 h period, T is the associated wave period, and g is
d
Eroding cliff
B
Beach
Ocean
h *1
h *100
L1
L100
Fig. 2. Illustration of the Bruun Rule
132
Clim Res 12: 129–136, 1999
the acceleration of gravity. The value of d (L,1) was
*
calculated for the various segments of the coast to
which the wave data refer. The wave data were also
obtained for 2 seasons and therefore d (L,1) was cal*
culated for the seasons and then averaged to give
d (L,1) = 2.84 m to represent the annual value. Using
*
this annual depth of closure, d (L,100) was approxi*
mated to be 4.97 m using the relationship in Eq. (2),
above.
It is worth mentioning here that a serious storm
surge occurred in July 1984 that resulted in waves
3 m high at the Vridi Canal and 3.5 m high outside
the Vridi Canal. Associated wave periods were 10.5
and 11.9 s, respectively (Cissoko Souleymane, Côte
d’Ivoire Oceanography Centre, pers. comm.). The
annual and 100 yr depths of closure for this rare
event in Côte d’Ivoire were calculated as 6.28 and
10.99 m, respectively, for the vicinity of the Vridi
Canal, and 7.39 and 12.93 m, respectively, for the
area outside of the canal. No wonder there was a
recorded loss of about 20 m of coastline around the
canal (Abe 1993, as cited in Abe & Lazare 1995) from
this phenomenon.
2.2.4. Flooding and increase in groundwater levels:
During the passage of West African disturbance lines
(squall lines) in The Gambia, the accompanying heavy
downpour causes flooding mostly in the capital city,
settlements established on reclaimed land in dried-up
valleys, and settlements that have been developed
very close to mangrove swamps and wetlands. These
are also the main areas where groundwater levels are
close to the surface and saline intrusion in groundwater is already a problem. The areas most affected are
the Half-die and Tobacco Road settlements in Banjul,
parts of Bakau, Old Jeswang, Eboe Town, Tallindiing,
Fagikunda, and Abuko.
The strength and frequency of tropical storms are
expected to increase with the expected climate change.
This will lead to more flooding, and the problem may
be exacerbated with sea level rise. Damage to structures such as buildings and roads will be the major
effect of the freshwater flooding.
2.2.5. Estimation of damage costs and population
at risk: A comprehensive evaluation of the economic
consequence of a 1 m sea level rise for both study
areas was not possible due to inadequate data and
limited resources. The evaluation was carried out
only for some important zones of the study areas.
The evaluation and analysis are based on socio-economic and demographic data collected during the
study.
The costs of damage or loss to coastal infrastructure,
such as roads, were also not evaluated. A quantitative
assessment of wetlands was not possible, as these are
not valued in monetary terms.
2.2.6. Limitations of the assessment: The study in
Côte d’Ivoire was constrained by lack of data, particularly economic data. AVVA was not conducted, and
characterization of the coastal zone was based on maps
that are more than 10 yr old. Even under such constraints, qualitative assessment has considerable value
in addressing the possible impacts of sea level rise and
climate change.
3. RESULTS AND DISCUSSION
3.1. Land loss on the open coast
In the coastal zones of The Gambia and the Abidjan
region, about 92 and 563 km2, respectively, are estimated to be inundated as a result of a 1 m sea level rise
(Table 1). The huge retreat of 563 km2 along the coastline of the Abidjan region is due to the fact that lowland marshes and lagoons dominate the coastal zone.
For The Gambia, shoreline retreat would vary along
the coast from 102 m in the harder cliffed zone
between Cape St. Mary and Fajara to 839 m in the gently sloping, sandy strand plain near Sanyang Point
(Table 2a). In the Abidjan region, average retreat due
to coastal erosion is estimated as 51 m and varies from
36 m around the coast of Abidjan to 62 m on the GrandLahou coast (Table 2b).
Table 1. Potential area (km2) of land to be inundated in the
coastal zone of (a) The Gambia and (b) the Abidjan region in
response to various sea level rise scenarios. Coastal units of
The Gambia: Unit 1 = Senegal Border to Barra Point; Unit 2 =
the Gambia River Basin; Unit 3 = Banjul Point to Cape St. Mary;
Unit 4 = Cape St. Mary to Fajara; Unit 5 = Fajara to Bald Cape;
Unit 6 = Bald Cape to Solifor Point; Unit 7 = Solifor Point to
Benchmark KM125; Unit 8 = Benchmark KM125 to Kartong
Point; and Unit 9 = Kartong Point to Allehein River
Coastal
unit
Sea level rise scenarios (m century–1)
0.2
0.5
1.0
2.0
(a) The Gambia
1
2
3
4
5
6
7
8
9
Total
0.56
0.94
1.56
0
0.01
0.41
0.27
0.03
1.19
4.96
(b) Abidjan region
Grand-Bassam
86.3
Abidjan
14.1
Jaquesville
1.9
Grang-Lahou
10.1
Total
112.5
14.06
23.40
3.90
0
0.03
1.01
0.67
0.08
2.69
45.89
215.9
35.2
4.9
25.2
281.3
28.12
46.87
7.80
0
0.05
2.03
1.34
0.17
5.93
92.32
431.7
70.5
9.7
50.5
562.5
56.25
93.75
17.63
0
0.20
2.89
1.81
0.17
8.85
181.55
863.5
141.0
19.5
101.0
1125.0
Jallow et al.: Sea level rise vulnerability of The Gambia and Côte d’Ivoire
Table 2. Application of the Bruun Rule to project land retreat
and rate of beach erosion on the open coasts of (a) The Gambia and (b) the Abidjan region in response to a 1 m sea level
rise. d* = depth of closure; G = overfill ratio; L = active profile
width; B = dune or cliff height; S = scenario; R = retreat of land
Coastal d*
unit
(m)
(a) The Gambia
1
5.9
2
3
5.9
4
5.9
5
5.9
6
5.9
7
5.9
8
9
Coastal
unit
G
L
Actual
(m)
B
(m)
S
Map
(cm)
R
(m)
1
3.5
2610.5
2.0
1
330.4
1
1
1
1
1
3.0
1.6
2.8
8.6
6.8
2284.2
1232.5
2080.8
6475.5
5098.3
2.7
6.1
2.7
1.8
3.0
1
1
1
1
1
275.6
102.2
264.1
839.2
597.2
133
tal city, settlements established on reclaimed land in
dried-up valleys, and settlements close to mangrove
swamps and wetlands. With an increase in strength
and frequency of tropical storms under a warmer climate, this phenomenon will increase. The problem
may further be exacerbated by sea level rise.
Only a small percentage of the population in the
areas obtain their water supply from local, shallow
hand-dug wells. The higher water table due to sea
level rise will exacerbate the existing problems of
salinization of the water supply. This situation is similar to that in the settlements surrounding the city of
Abidjan due to the presence of lagoons.
3.4. Estimates of damage costs and population at risk
d*
(m)
(b) Abidjan region
Grand-Bassam
4.97
Abidjan
4.97
Jacqueville
4.97
Grand-Lahou
4.97
Average retreat
G
L
Actual (m)
B
(m)
S
R
(m)
1
1
1
1
372
238
380
340
2.0
1.6
2.0
0.5
1
1
1
1
53.1
35.6
54.4
61.8
51.2
3.2. Estimation of land loss on the sheltered coast
In the sheltered coast of The Gambia, we consider
only the low-lying mangrove systems and adjacent
marshland and agricultural lowlands. These systems
extend to about 200 km from the mouth of the river,
and hence wave action is not critical. As shown in
Table 1a (Unit 2), about 50% (47 km2) of the total land
loss due to inundation comes from the sheltered coast.
The effects of sea level rise on mangroves depend on
the extent to which the mangroves continue to receive
sediment. Where there is little or no sediment supply,
submergence is likely to cause dieback and erosion of
their seaward margins. In a natural environment,
mangroves can still spread landward, displacing the
low-lying hinterland. However, the mangrove systems
bordering Banjul, Bakau, Old Jeswang, Eboe Town,
Talinding Kunjang, Fajikunda, and Abuko have all
their hinterland reclaimed for settlements, and thus the
mangrove fringe and the adjacent agricultural lands
have become narrower and will eventually disappear
as the sea level rises. This will lead to a loss of a large
area of wetlands and fish spawning grounds.
3.3. Flooding and increase in groundwater levels
Heavy downpours of rain that accompany squall
lines during the wet season cause flooding in the capi-
With a 1 m sea level rise, it is evident that the whole
of Banjul, the capital city of The Gambia, will be lost
because the greater part of the city is below 1 m above
sea level, as shown in Fig. 3. The mangrove systems on
St. Mary’s Island, Kombo St. Mary, and the strand
plains in the north bank from Barra to Buniadu Point
will be lost.
The entire population of Banjul (42 000 inhabitants),
people living in the eastern parts of Bakau and Cape
St. Mary, and the swampy parts of Old Jeswang, Kanifing Industrial Estate, Eboe Town, Tallinding Kunjang,
Fagikunda, and Abuko will be displaced. About 1950
billion Dalasis (US $ 217 million) worth of land will be
lost. All the structures located on the land area from
Sarro to the Banjul cemeteries will be lost.
Although some important areas of Abidjan lie on a
plateau and may escape the direct effects of a 1 m sea
level rise, major economic centres of the region, such
as the Port of Abidjan and the international airport at
Port Bouet, will be severely affected as most of the land
is equal to or less than 1 m above sea level. The element of the infrastructure that is most threatened is the
Autonomous Port of Abidjan (Port Autonome d’Abidjan, PAA), which contributes more than 68% of the
importation into and 60% of the exportation from
the country (PAA 1996). It has about 5 km of quays
(29 quays); 28 depots for goods; 11 other specialized
depots for fertilizer, phosphates, and hydrocarbons;
a container terminal for fruits, vegetables, timber,
and oil; a fisheries port; and so forth. PAA has over
140 000 m2 of hangers and stores, 770 ha of industrial
zone, and over 360 000 m2 of terraces.
This entire infrastructure is currently threatened by
an erosion rate of about 2.4 m annum–1, and when the
sea level rises by 1 m within the next century most of
the area will be inundated. This inundation will be
followed by a retreat of the land by another 11.5 m due
to erosion to the east of the Vridi Canal. The present
134
Clim Res 12: 129–136, 1999
ven into the beach and tied
together with timber. They are
also constructed from reinforced
1.5
concrete, as on the Maputo
0.5
1.0
shoreline in Mozambique. They
are easy to build, are fairly cost
effective, and locally hold the
0.5
beach or capture more sand in
the longshore sediment transport
2.0
1.5
(LST) system. They do not ‘create’ new sand but merely redistribute the sand along the beach.
Groins have been found to be
very effective in stabilizing eroded beaches particularly in the
Republic of Togo, West Africa
1.0
(Blivi 1993).
This response strategy is recommended for the coast of the
1.5
Abidjan region, particularly east
2.0
1.0
of the Vridi Canal. In The Gambia,
the existing groins in the area be1.5
tween the Laguna Beach/Palm
2.0
Grove hotels and Banjul Point
(Fig. 4) need to be rehabilitated.
To reduce the flow of sand to the
port and ferry terminal, a long and
high terminal groin must be
Fig. 3. Orthophoto map of the city of Banjul (the greater part of the city is below 1 m)
constructed at Banjul Point. This
terminal groin must not be filled
with sand so that the longshore sediment transport is
erosion rate is due mainly to the construction of moles
halted or reduced for some period of time.
on both sides of the canal and a breakwater on the
Another shoreline stabilization technique that could
western flank of the canal. This breakwater traps most
be useful in the protection of the sandy beaches of The
of the longshore sand coming from the west. This has
Gambia and the Abidjan region is the breakwater
led to an accretion rate of 2.3 and 4.6 m annum–1
system (Fig. 5). Breakwater systems have the ability to
between 1975 and 1985 and between 1985 and 1996,
reduce the strength of breaking waves coming onrespectively, on the western side of the canal.
shore, reduce the impact of waves on the shoreline,
and thus reduce the quantity of sand eroded.
4. RESPONSE STRATEGIES AND
ADAPTATION OPTIONS
2.0
4.1. Response strategies
In both study areas, the suggested response is to protect only the important areas. For The Gambia, these
are the areas between Banjul and Cape Point and
areas around the hotel complex from Kairaba to Kololi
Beach Hotel. For the Abidjan region, the important
areas are the major cities of Grand-Lahou, Abidjan,
and Grand-Bassam. The following shoreline hardening and stabilization techniques could be used to protect these area.
Groins are a major technique of beach stabilization
in Africa, whereby trunks of rhun palm trees are dri-
Fig. 4. Damaged groin system that has protected the City of
Banjul for more than 40 yr
Jallow et al.: Sea level rise vulnerability of The Gambia and Côte d’Ivoire
135
and the city of Banjul. This would, however, result in
the flow of a large unwanted quantity of sand to the
Banjul-Barra ferry terminal and the Gambia Ports
Authority facilities, the solution to which is suggested
above—that is, constructing a long terminal groin at
Banjul Point.
Also, to protect the area between the cold storage
plants west of the Public Works Complex (National
Partnership Enterprise and Pelican) and the Gambia
Senior Secondary School, and areas bordering the
mangrove systems, it is sufficient to use dikes made up
of about 1.5 to 2 m of sand on which some vegetation is
planted.
4.2. Adaptation options
Fig. 5. Breakwater system for reduction of erosive wave energy
Revetments are also useful in reducing erosion but
need proper construction to be effective. They are
expensive, and in most cases the beach is lost. Revetments consist of a layer of large boulders on the
seaward side and a layer of filter screening material on
the landward side. Theses 2 layers are separated by
another layer of medium-size gravel that is used to protect the screening material (Fig. 6). The voids in the
structure of the outer layer on the seaward side are
used to dissipate wave energy; the filter screening
material of the landward layer allows water to pass
through. It may be sufficient to build only a low-cost
seawall or a bulkhead.
Particularly for The Gambia, it may be necessary to
employ an innovative sand management approach to
solve the large erosion problem between the NAWEC
(National Water and Electricity Corporation) water
tanks and Banjul Point. This could be achieved by
tying the end of the sand spit off the Palm GroveLaguna Beach hotel complex (Fig. 7) to the mainland
so that it becomes a sand-feed to the area to the east
Fig. 6. Cross-section of a revetment
4.2.1. Public awareness and outreach activities
These activities would inform the public of the danger of living in coastal lowlands that are at risk of being
affected by sea level rise. Timely public education
about sea level rise impacts and risks could be a costeffective means of reducing future expenditure.
4.2.2. Increase in height of coastal infrastructure and
urban growth planning
Physical planning and building control measures
and regulations should be instituted and implemented.
The land, physical planning, and building control institutions of The Gambia and the Abidjan region should
Fig. 7. Sand spit at the Palm Grove/Laguna Beach Hotel
complex
136
Clim Res 12: 129–136, 1999
avoid allocation of land that is likely to be flooded,
such as the dried-up streams on the Kombo Peninsula,
which have recently witnessed flooding during the
rainy seasons of the late 1980s and the lagoon areas of
Abidjan.
Where the building of coastal infrastructure such as
roads, fish landing sites, and curing plants are approved and must be put in place, the authorities and
owners of these infrastructure elements should make
sure that marginal increases in the height of the structures are included to account for sea level rise and
any other related phenomena. Siting of large capital
facilities or those that pose significant hazards when
flooded should not be allowed in sensitive lands and
must be directed toward less vulnerable areas. People
located in high-risk areas should be offered incentives
to relocate out of these areas. Policies should be instituted that allow the use of high-risk areas as natural
preserves or for low-value use.
Marginal increases in the height of the infrastructure
elements during construction phase and redirecting
growth away from sensitive lands are relatively inexpensive options for reducing the impacts of sea level
rise and risks of flooding. Policies that may lead to relocation from high-risk areas will reduce the need and
cost of disaster relief in the future.
4.2.3. Wetland preservation and mitigation
The estuary of the River Gambia and lagoons of the
Abidjan region contain economically important wetlands and mangrove systems. The mangrove systems
on the Kombo St. Mary Island and Kombo Peninsula
are important breeding grounds for various aquatic
species. Efforts should be made to protect these areas
by declaring them protected wetlands. This would
discourage exploitation of the resources in these wetlands. The possible impacts of upstream dams on the
River Gambia in terms of reduced sediment supply
should be investigated.
4.2.4. Coastal zone management plan
Land-use planning in coastal zones, such as using
building setbacks or allocating low-lying vulnerable
lands to lower value uses (for example, parks rather
than housing), will help reduce the overall vulnerability to sea level rise. Other land use planning mecha-
nisms, such as construction standards, reduce the risks
of living in coastal areas. Additional risk-reduction
measures can be encouraged through appropriate
financial mechanisms. Each of these policies reduces
the risks from current climatic variability and protects
against potential sea level rise impacts. When put
together in the form of a programme, they constitute a
coastal zone management plan.
Acknowledgements. This study was funded by the US Country Studies Program (USCSP). Mr Robert K. Dixon is the Program Director and Ms Sandy Guill is the Project Officer for
The Gambia and Africa. Presentation at the workshop was
made possible through the funding from the United Nations
Environment Programme (UNEP), the Netherlands Climate
Change Studies Assistant Programme, and the USCSP.
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